Television apparatus and system



` Aprnl 16, 1935. J. GETTINGER 99823 TELEVISION APPARATUS AND SYSTEM Filed June les, 1952 6 sheets-sheet 1 M5230? 67e/ ye);

ATTQRNEYG l vv Www 6 ovm n M\\ u Pril 16, i935 J. GETTINGER TELEVISION APPARATUS AND SYSTEM Filed June 16, 1932 y6 Sheets-Sheet 2 INVENTOR J@ 662% er' April 16, 1935. GETTINGER 1,998,23

TELEVLQION AEPARATUS AND SYSTEM Filed June 16, 1932 .s sheets-sheet 5 INVENTOR @9.9, EY f? ATTORN EYS plE i5, l935, J. GETTHNGER TELEVISION APPARATUS AND SYSTEM Filed June 16, 1932 y6 Sheets-Sheet 4 INVENTOR ATTORNEYS vApril 16, 1935. n GETTHNGER ,1998,23l

` TELEVISION APPARATUS AND SYSTEM INVENTOR ATTORNEY INVENTOR ATTO RN EYS pril 16, 1935..

J. GETTINGER TELEVISIONAPPARATUS AND SYSTEM Filed June 16, 1932 6 Sheets-Sheet 6 Patented Apr. 16, 1935 STTES PATENT FFICE 6 Claims.

The present invention pertains to a novel television apparatus and system, either wired or wireless, and the principal object is to provide successive, complete images rather than a scanned image at the receiving end. In keeping with this general object, the apparatus is adapted to produce lrn exposures in the receiving apparatus, and although these exposures are produced by scanning in synchronism with a scanning disk at the transmitter, they are projected as cornplete images in rapid succession upon a screen after the fashion of a motion picture projector. The rate of projection in motion picture work is approximately sixteen exposures per second, and accordingly, the device of this invention is adapted to make a similar number of exposures per second and throw them upon the screen.

Another object of the invention is to do away with the shutter which has hitherto been found necessary during shifting of the lrn in motion picture work. According to the invention, the apparatus is so constructed that the photoelectric cell at the transmitter received no current while the rllrn in the receiving set is being shifted, and

the same time the projector lamp is extinguished, so that no light is projected through the film and no shutter is therefore necessary during shiitlng of the film.

Another object of the invention is to dispense with synchronous motors in the transmitting and receiving sets. In the receivinCT set, the ilrn actuating mechanism is permanently timed and synchronized with the nlm developing means, and the speed of the latter is regulated from an adjustable speed motor until a clear image is pro-- jected.

The film developing means is an electrical apparatus adapted to scan areas of the film with electrical discharges which vary in their properties according to the light received at the photoelectric cell. The film is of such a nature as to react tc these discharges to reproduce thereon the nature of l ght impressed upon the cell. The film areas thus exposed. to the electrical discharges are instantaneously developed and, as already indicated, projected upon a screen, from a projector embodied in a receiving instrument.

Still another object of the invention is tc proa concurmt sound record with the nlm record. Ordinarily, the event being broadcast 'oy television may also 'ce broadcast visually by radio, cut since the picture film is adapted to oe used repeatedly, it is desirable to have a sound record for such repeated showings. Accordingly, the receiving instrument contains a sound recording apparatus which is sensitive to a radio broadcasting station at the television transmitting station. The sound recording instrument may 'be used at the option o the owner. For recording the sound, there is employed a sound iilm sensitive to electrical discharges somewhat similar to those already described and which is driven in synchronism with the picture lin in the receiving instrument. In making a subsequent showing oi the picture lrn, both the picture and sound nlrns are obviously run synchronously through a projector and a sound reproducing machine respectively.

The invention is fully disclosed by way of example in the following description and in the accompanying drawings, in which- Figure l is a vertical section of the camera;

Fig. 2 is a plan section of the photoelectric cell;

Fig. 3 is an enlarged detail in the same plane as Figure 1;

Fig. l is a plan section of the photoelectric cell,

showing several planes thereof;

Fig. 5 is a vertical section, partly in elevation, of a modified form or" photo cell;

Fig. 6 is a diagram showing the relation between the current frequency and the scanning disk speed;

Fig. 7 is an elevation of the camera, showing particularly the scanning disk and the means for driving the same;

Fig. 8 is a detail plan section of the scanning disk and camera parts;

Fig. 9 is a vertical section of the receiving instrument;

Fig. 10 is a diagram of the camera and transmitter;

Fig. 1l is a diagram of the receiving set;

Fig. 12 is a detail plan section on the line i2-l2 of Figure 9;

Fig. 13 is a detail elevation in the plane |3--l3 of Figure 9;

Fig. 14 is an elevation of the contact disk of the receiving instrument;

Fig. 15 is a detail thereof, partly in section;

Fig. 16 is an enlarged detail on the line Ie--IB of Figure l5;

Fig. 17 is an enlarged detail on line l'I-ll of Figure 15; and

Fig. 18 is a developed plan section of the commutator.

Reference to these Views will now be made by use of like characters which are employed to designate corresponding parts throughout.

In Figure 1, the camera or instrument which makes the first impression is shown as comprising a housing consisting of a pair of spaced frame members I secured together by channel members 2. The frame thus formed supports a cylindrical light-proof casing 3. rI'his structure rests on a base t and is maintained in upright position by suitable props 5 and 6.

To the centers of the plates I are secured bearings l in which is journaled a shaft 8. An electric motor 9 is mounted on the base and is connected to the shaft by a chain I@ or other suitable driving means. On the shaft 8 and within the liner 3 is secured a scanning disk II formed with a spiral series of apertures I2 therethrough.

In one of the plates I and opposite the apertures part of the scanning disk is mounted a light tube I3 which may be equipped, if desired, with a lens system Ill.. The light tube is exposed to the object whose image is to be transmitted, and this object may be illuminated inra manner well known in the television art.

The opposite disk I supports a photoelectric cell positioned t0 receive the light rays which are passed from the tube I 3 through the apertures I2. The cell is. enclosed in an insulating housing I 5 secured to the plate I and includes a heavy insulating lining I6 within the housing. Into. the housing is tted a block Il of pure metal and of substantially cubical formation, leaving however a vacuum space It adjacent the disk II. A screen I9 is stretched across the vacuum space and is joined by a conductor 2t to the amplier of the broadcasting apparatus as will presently appear. The forward or open face of the vacuum space I8 is sealed by a glass plate 2i adapted to transmit light rays from the apertures I2 without distortion. In this connection it is to be noted that the plate 2I consists of glass which is so placed as to have a grain parallel to the aperturesv I2.V Also, the apertures I 2 have a length at least sixteen times their diameter, for optical eiciency and accuracy in the passage of the light beam therethrough.

The face of the block Il' at the vacuum space I8 is coated with an alkali metal 2G whereby emissions are delivered therefrom when a light beam is received during a negative current charge in the block. A triangular shaped conductor 21 is mounted at that side of the space I8 toward which the disk II rotates. This block is the collector of the emissions and transmits them to the conductor ZIE as shown in Figure 4l. The conductor 2l is secured to the screen I9, and the trianguiar shape thereof is conducive to perfect transmission of the emissions over the circuit, as will be described in another application.

In Figure 5 is shown a modified form of photoelectric cell wherein the screen is replaced by a gas-filled space 28 serving as a part of the system for conducting the emissions delivered from the metal block Il. Around the border of this space is mounted a frame 29 having an enlarged side 35 of triangular cross section, connected to the conductor 2li' leading to the amplifier. The part 3B is positioned at the side of the space toward which the scanning disk rotates and functions in the same manner as the member 2l of Figure e. u Figure 6 illustrates diagrammatically the travel of the apertures I2 across the photoelectric cell. Although the light passes in lines across the cell, spots of light 3l are illustrated in tangential relation in Figure 6. In the time that a spot of light travels a distance equal to its diameter, it is desired that at least two impulses occur in the current passing through the cell, in order that the lineof light may be finally subdivided in the amplier and broadcasting circuits and picked up in the same state of subdivision at the receiving instrument, as will presently appear. In the apparatus shown, a spot of light traverses its diameter in l/ 126 thousandth of a second, and consequently the frequency of the current is 252 kilocycle per second.

It is also to be noted that the spacing of the apertures I2 in the disk II is only slightly less than the width of the sensitive part of the photoelectric cell, so that a given aperture will not commence its travel across the cell appreciably before the preceding aperture has completed itsy travel across the cell. The spacing of successive apertures radially of the disk is slightly less than the diameter of the apertures to afford a slight overlapping of light paths across the tube I3 and thus assure complete covering of the object to be transmitted.

The current established in the conductor 2d by the emissions of the cell is induced by means of coils32 into an amplifying system 33, the rst stage of which is indicated by the numeral 3&3. From the amplifying system, the current is delivered to a grounded transmitter 35 and thence to an aerial S5 from which it is broadcast.

The receiving instrument is built in a housing IIB and includes a pair of supporting plates il carrying a pair of roller bearings l2 in which is journa-lled a shaft 43. a disk Ificarrying a spiral series of electrodes 55 spaced in the same angular sequence as the apertures I2 of the disk II. A motor l mounted in the housing drives the shaft through a chain Ill.

One of the plates II supports an insulating housing 4S in which is mounted an electrode block 139 adapted to be scanned by the free points of the spiral series of electrodes L35. An arm Sil extending from the plate 4I supports a reel 5I on'which is wound a lm E2. This film is passed between the housing 48 and the supporting plate II and is exposed to the electrodes through an aperture 53 in the plate. The lm is then carried through a projector 5t and is finally wound on a take-up reel 55.

The radiations from the aerial 36 are received, as shown in Figure ll, by an aerial 5E connected successively to a receiving set 51, amplifying systern 58 and a high voltage transformer 59 such as a Tesla coil. With reference again to Figure 9, the outward terminals of the transformer @Il are connected respectively to the electrode 49 by a conductor 6I! and to a commutator system at the disk fill, presently to be described, by a conductor 6 I. High voltage discharges corresponding to the emissions from the photoelectric cell are thus produced from the electrodes it to the block i9 and through the lm, producing on the latter successive pictures while the film is stopped intermittently at the block dii. The film is advanced intermittently to the projector 544 and wound up on the spool 55, so that the reception is in the form of a motion picture rather than a scan picture as in the present television devices.

With reference now to the details of the electrode disk 44, each electrode t5 has a conductor $2 extending therefrom to an insulating ring S3 mounted concentrically on the disk. The inner ends of the conductors are rst directed into the ring as at lill, and then circumferentially of ring, as at 65, beneath a peripheral groove 55 cut in the ring. A bell crank lever is mounted on one of the plates III, and to one of its arms 6l is secured a Contact member beneath which tl c segments 65 are adapted to rotate in sliding con- On the shaft is mounted n i.' un

tact therewith. A spring 69 draws the 'other arm 'l0 of the bell crank upwardly and thus holds the contact 5S in resilient engagement with the segments $5. yThe segments, moreover, are insulated from each other by means of mica inserts il. VThe conductor 6l from the transformer iiii is joined to the contact member 68 as may be seen 'in Figure 9.

The film 52 unwinding from the reel 5i passes first between a pair of guide rollers 'i2 and then through a pair of 180 cams 13. These cams are so positioned relatively to each other that the high points thereof are concurrently in engagement with opposite sides of the lrn 52, or during an interval of 180 of rotation. During the remaining half of each revolution, the nlm is relieved of any driving action by the cams. Gn leavingtlie projector Effi, the film passes between a pair of similar cams 'la and then through a final pair of guide rollers '55, from which it is wound up on the reel The cams "M are in synclironism with and operate in the saine manner as the cams '33, cooperating therewith in intermittently moving the film during actuation thereof by the mechanism which will now be described.

Gne of the ends of the shaft i3 carries a bevel gear 'it adjacent which is a bracket Ta' supporting another gear i8 meshing with the gear iii. A vertical shaft 'it carries at one end a bevel gear 8f! meshing with the gear 18.

The shafts i3 (Figure i2) on which. the cams Z3 are mounted carry meshing gears el, and one of these shafts carries a bevel gear 82. A horizontal shaft 83 suitably journalled in the housing carries a bevel gear 84 meshing with the gear 82 and still another gear 85 meshing with a beveled gear 8E on the upper end of the shaft i9. Another vertical shaft t? is mounted in line with the shaft T9 and carries at its lower end a gear 38 meshing with the gear 35. The upper end of this shaft carries a bevel gear 89 which is operatively connected to the cams 'i4 through gearing 96 similar to that which extends from the gear 86 to the canis i3. a gear drive is established from the shaft 423i to both pairs of cams 'i3 and M, operating the latter in the manner already described.

At selected points along the length of the nlm 52 between the spools 5l and 55 are mounted devices foi holding the nlm in a iixed and taut condition while it is stationary. This means consists cf two or more electro-magnets Si having spring pressed plungers 92 which normally press the film against stops 93 when the magnets are de-energized. The conductors ed which supply current to the magnets pass through a switch consisting of a fixed contact 95 and a movable contact 95. Similarly the conductors Si for supplying current to the projector lamp 93 pass through a switch comprising a fixed contact 99 and a movable contact Hill.

The switches are mounted on a frame piece ll carrying a pair of gears IU?. and m3 meshing with a pinion H34 on the shaft #13. The gears |82 and m3 rotate with cams imi and it acting on spring pressed plungers itl and liiS adapted to close the normally open switches previously described. It will be seen that the switches are oppositely disposed, that is, the magnet switch is open while the lamp switch is closed and vice versa. The cams lil and 06 are so related to the switches and to the film feeding gear that the magnet circuit is open to release the film while the latter is being ied by the cams 13 and 15, at which time the lamp circuit is open.

Conversely, when the hlm is not moved by the cams i3 and i5, the magnet switch 8i. e6 is open to permit the plungers 92 to hold the film against the stops 93, at which time the lamp circuit is closed.

Itis not necessary to synchronize the motor 66 with the motor S as in conventional television apparatus. A suitable adjusting means on the motor S is utilized to vary the speed thereof until a clear picture is projected. The film feeding means is timed with and geared directly to the disk, so that no separate adjustment thereof is required.

The commutator mechanism including the seg.- rnents 65 an contact blade 58 permits flow of current only to the particular electrode IE5 which is travelling across the lin at any given instance. As already indicated, the portion ci iilni at the block d is developed by the action of the spark discharge therethrough, intensied by the high voltage coil E33. This action causes a chemical and thermal action on the film, and tlie character of the nlm is such that by this action a picture is instantly produced thereon.

More speciically this filni is composed oi a material of an absorbent character. Such material may consist of cellulose similar to the ordinary Celluloid hn or a product made from cellulose. This nlm is impregnated with glycerine which owing to its hygroscopic and liydrolizing proporties has a certain moisture content whereby said film is rendered conductive to a spark discharge of a. predetermined voltage and current. Other substances having similar chemical characteristics may be substituted for the glvcerine.

Incorporated with the glycerine are certain dye or coloring substances normally opaque to light. The passage of a spara discharge across and through this nlm alters the chemical and physical structure of both glycerine and the dye or coloring matter in ccordance with the varying intensity of the discharge which is determined by the intensity ci light impinging on the photoelectric cell.

Further, this dye mattei' when subjected to a spark discharge of varying intensity is thereby rendered more or less transparent due to a chemical change in the glycerine and its reaction upon the dye or coloring matter. This action instantaneously conditions said :film whereby successive portions of said film are permanently altered chemically and physically to permit more or less light to be transmitted therethrough. Said film is then ready for immediate passage through the picture projector.

The physical dimensions of the film is such as to provide a high resistance which permits the use of a voltage ci" high intensity and low current flow in order that each peak spark discharge shall only aiect a minute portion of the film at any one instant.

The value of this resistance is such as to dcvelcp a varying quantity oi heat which is proportional to the varying intensity of spark discharge which effects a chemical change in the glycerine whereby acetic acid is produced in vary ing amounts per unit of time.

The reaction. oi" this acid upon the pigment of the dye substance (which is normally opaque) together with the effect oi the ozone produced by the spari; discharge and its intense oxidation property affects both the glycerine and dye substance causing a permanent change therein. This change is continuous and affects the transparency of the dye substance in varying degrees which permits the transmission of more or less light therethrough and which is in correspondence with the intensity of the light variation impinging on the photo-electric cell.

The temperature and heat developed by the spark discharge is of instant duration and of high lfrequency and said heat is wholly absorbed in the chemical reaction. Thus the material of the lm itself and its inherent transparency remains unchanged.

The resistance of the lm is determined by the degree of moisture content in the glycerine, and upon this depends the voltage and curr-ent required.

In this manner a iilm is produced having a texture similar to that of a photographic negative in that varying degrees of transparency between the high lights and deep shadows thereof are produced byy the progressive movement of the electrode across the illm whereby corresponding changes in the dye matter occur in accordance with the varying intensity of the spark discharge.

While the above results are obtained by the spark discharge through a conductive lm similar results may be obtained electrostatically from a glycerine-color combination layer applied to the surface of a transparent nlm. This iilm is of a high insulating character and in this capacity provides a dielectric between the electrode and block, these constituting the plates of a condenser.

Varying potentials applied across said electrode and. block cause a change in the glycerine-color layer in a manner similar to that caused by a spark discharge through the conductive impregnated lm. Moreover, the impregnated lm may contain a plurality of `colors which are either eradicated or toned selectively in accordance with characteristics of the spark discharge determined by the color of light impinging on the photo electric cell. The lm is continuously impregnated and the pictures are localized thereon by the intermittent motion of the i'llm.

if the apparatus is intended to make, for example, fteen exposures per second, the disk ifi is geared to make thirty revolutions per second, since the apparatus yis rendered optically and photographically inactive during alternate rotations of the disk t@ to permit shifting of the nim between exposures. lIt is evident that the photoelectric cell must likewise be inactive during corresponding, alternate revolutions of the disk Il, and this action is accomplished for both disks by the mechanism shown in Figures l and l0. The conductor 2li in the circuit between the power source 25 and the photoelectric cell contains a normally open switch comprising a xed contact H39 and a movable contact H0. Adjacent thesel contacts is a bracket i l i supporting a shaft l l2 which carries at one end a gear l i3 meshing with a pinion lill on the shaft 8. The other end of the shaft l l2 carries a cam i I5 adapted to move a spring pressed plunger H6 into engagement with the movable contact HG to close the circuit. This cam is constructed in such a manner as to hold the switch closed on alternate revolutions of the shaft 8 and permitted to open on the intervening revolutions. inasmuch as this switch controls the emanations from the transmitter 35, it also determines the operative and ideal paths of the receiving instrument.

In transmitting an animated scene by this apparatus, a conventional radio outiit may be used in conjunction therewith for transmitting the accompanying sounds. The sound would ordinarily lag behind the projection of the scene from the projector 51% due to the difference between the speeds of sound and light in travelling from the scene to the transmitting apparatus. This lag is compensated to a great extent by the interval of time required for the travel of the exposed nlm section from the block 59 to the projector 54. It will be seen in Figure 9 that this distance is approximately twice the length of a nlm exposure, so that if the receiver makes teen exposures per second and the disk turns thirty times per second, the interval between exposure and projection will be two-thirtieths of a second.

The nlm is a permanent record and may be used repeatedly, in which case an accompanying sound record would be desirable. A sound record may be made concurrently with the first nlm record, at the option of the owner of the receiving set, and mechanism for this purpose is therefore provided in the receiving set. A radio broadcasting station 52e is erected at the scene to be reproduced, as shown in Figure i6, and the message therefrom may be picked up by a receiver lZ associated with the receiving set as illustrated in Figure ll. lThe receiver l2l is connected to an amplifier E22 and then to a current interrupter l 23 and a high frequency transformer IM similar to the member 59 of Figure 9. The interrupter has a power input 25 as shown in Figures 9 and il. The output lines iii and l2? from the transformer 12d lead respectively to a knife-edge electrode E23 and an opposed surface electrode H29 supported in a bracket 35. The arm 50 carries a reel l 3i on which is wound a sound nlm 132. The film is drawn through a guide 35 across the face oi the electrode 29 and wound on another reel i3d suitably mounted in the housing. The upper end-of the shaft 8% carries a pair of pulleys l35 and 35 connected respectively by belts i3? and 138 to the .reels 55 and 3ft so that the latter are turned togetherand in deiinite relation to the disk s.

The shaft 83 is extended through the bracket S33, as shown in Figure l2, and carries a bevel pinion H39 adjacent the guide 33. A pair of shaf ts lfiii are journalled in the bearing and carry rollers lli! engaging opposite sides of the lm 532. The shafts also carry meshing gears liZ, and one of the shafts carries still another bevel pinion M3 meshing with the pinion E39, whereby the friction rollers lli! are driven from the shaft 83. A similar shaft and roller mechanism indicated generally by the numeral Mii in Figure 9 is mounted in the upper part of the bracket |30 and connected to the shaft 83 by a sprocket chain E135. The sound nlm is thus propelled in synchronism with the picture nlm 52. This apparatus may be cut out, when desired, by means of a clutch 83' in the shaft 33.

By reason of the interrupter 23, an intermittent current is delivered to the electrodes |28 and E29, and the transformer H24 causes this current to produce high frequency and high voltage electrical discharges through the nlm E32. Variations in the intensity of the. discharges are produced by variations in the sound at the source and in turn result in variations in the impressions or reactions produced on the film E32. The lm may then be passed through a suitable sound reproducer to reproduce the original sound simultaneously with a showing of the nlm 52.

The casing d@ of the receiving instrument requires circulation of air therethrough because of the ozone and other chemical products produced by the electrical discharges upon the iilms and also for cooling purposes. Accordingly, an open- Cil ing M6 is made near the bottom of the housing and covered with a screen ld? to prevent interference, the housing being grounded as at itil. A suction tube i453 is inserted at the upper end of the opposite wall of the housing and is connected to any suitable suction apparatus, whereby a circulation of air through the housing is produced.

It will be readily understood that the system and apparatus described herein may be used in a wired circuit as well as in a radio circuit. An example oi the utility oi the invention in a wired circuit is in the sendng of photographs over telegraph wires in newspaper work, and in this connection a photograph may be transmitted by means of the invention in a small fraction of the time ordinarily required.

Although specific embodiments of the invention have been illustrated and described, it will be understood that various alterations in the details oi construction may be made without departing from the scope of the invention, as indicated by the ap oended claims.

What I claim is:-

l. A television receiver comprising means for receiving current impulses from a photo-electric cell, mean-.s for supporting a lni, means for cone erting the said impulses into electrical discharges and for passing said discharge through said in a two-dimensional pattern, a projector, and means for moving said intermittently through said projector, electro-magnetic holding means for engaging said hlm between movements thereof, and switching means operable by said electrode dish for releasing said holdino` means from said film during movements or the latter.

2. A television receiver comprising means for receiving cur ent impulses -from a photo-electric cell, means ior supporting a hlm, means for converting the said impulses into electrical discharges and for passing said discharges through said nlm in a two-dimensional pattern, a projector, cams adapted to engage opposite sides oi the iilm and to feed the hlm intermittently to said projector, said cams being geare to said electrode disk, electro-magnetic holding means for engaging said film between movements thereof, and switching means operable by said electrode disk for releasing said holding means from nlm during movements of the latter 3. A television receiver comprising means `for receiving current impulses from a photo-electric cell, means for supportinrf e, hlm, means for converting said impulses into electrical discharges and for conducting said discharges through said nlm in a two-dimensional pattern, said film comprising a glycerine content having a color medium therein susceptible to change due to a varying electrical discharge to permanently alter the tone of said color medium in accordance with the intensity of the electrical discharge, a projector, and means for moving said lm intermittently through said projector, electro-magnetic holding means for engaging said film between movements thereof, and switching means operable by said electrode disk for releasing said holding means from said lm during movements of the latter.

A television receiver comprising means for receiving current impulses from a photo-electric cell, means for supporting a iilin, means for converting said impulses into electric discharges and for conducting said discharges through said lm in a two-dimensional pattern, said iilm comprising a glycerine content having a color medium therein susceptible to change due to a varying electrical discharge therethrough which permanently alters the tone of said color medium in accordance with the intensity of the electrical discharge, a projector, cams adapted to engage opposite sides of the nlm and to feed the film intermittently to said projector, said cams being to said electrode disk, electro-magnetic holding means for engaging said nlm between movements thereof, and switching means opera le by said electrode disk for releasing said holding means from said film during movements oi the latter 5. A television receiver comprising means for receiving current impulses from a photo-electric cell, means for supporting a film, means for converting said impulses into electrical discharges for conducting discharges through said a two-dimensional pattern, said film com- -dium therein susceptible to change due to a ying electrical discharge to permanently alter tone oi said color medium in accordance with intensity of the electrical discharge, a. profor moving said nlm intersaid projector, electro-mag- 'c holding means for engaging said film be- Ven movements thereof, and switching means operable by said electrode disk for releasing said holding means from said iilm during movements or the latter.

6. A television receiver comprising means for receiving current impulses from a photo-electric cell, means for supporting a lm, means for converting said impulses into electric discharges and for conducting said discharges through said lm in two-diznensional pattern, said nlm comprising a hygroscopic medium having a color medium therein susceptible to change due to a varying electrical discharge therethrough which permanently alters the tone of said color medium in accordance with the intensity oi the electrical discharge, a projector, cams adapted to engage opposite sides or" the nlm and to feed the film intermittently to said projector, said cams being geared to said electrode disk, electro-magnetic holding means for engaging said film between movements thereof, and switching means operable by said electrode disk for releasing said holding means from said lm during movements of the latter.

JOSEPH GETTINGER. 

